Carbs & carb rebuilding


New member
I have the Bentley manual on order. I was wondering if you could give me some suggestions for revamping or replacing my current dual carb setup on a 73 bus. It has Dellorto carbs running on a stock(as far as i know)1700 engine. The carbs are not running well despite attempts at adjusting them and having a professional do so. At this point I'm considering rebuilding the Dells,or buying the stock carbs(kadron/solex 34's, I believe) or weber 34's. Please let me know the wisdom/feasability of returning to the stock configuration.
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New member
Thanks for opening up this discussion. I am in the same situation. My VW mechanic is suggesting to get "new" carbs for my 74 bus with a 1800 stock (I belive) in it, but it cost lots of money, and I don't even think it is an option to buy new stocks.
I've heard that you can get a re-build kit for them, but also that there is a company in CA that "rebuilds" the bottom butterfly value that would make them run better?? Company called Rimco Machineing?
My bus is in Minnesota and I also need advice on cold-weather running/starting. For I am getting mixed options on choke/no choke. John Muir in his book hates them, but in CA it is warm. Also my air cleaner and "balance tube" (the rod that is in between the carbs) are missing. Are these something I need to invest in for quality running?
Thanks for opening up this carb discussion...very important!!!
In peace...Jason

Capt. Mike

kevglorde:Although the Bentley is expected for response on this site (Message Board Guideline #2) it will not carry information on aftermarket carbs & conversions. It's OEM carb rebuilding section is very complete.

Per Guideline #6, few are likely to have much experience or resources to assist you with aftermarket conversions. You might look at the CONVERSIONS forum where there are some discussions on carb options that may include some useful info.

The original stock carbs provided excellent performance and reliability. The complaints you hear are almost always from those unable or unwilling to learn the carbs and their adjustment. OE carbs were set up to a purpose -- a good compromise between performance, reliability and fuel economy while meeting EPA requirements. Some who swap are willing to compromise one or the other for their personal preferences. Returning to stock carbs gets you both OE performance and OE resources, including advice and assistance on this site.

Jason P: There is no free lunch and thus no 'free' carb solutions. The fuel system is one of the most expensive parts of a power plant and repairing it will be proportionally expensive. Without seeing the carb, no one can confirm your mechanic's suggestion of "get new carbs" but that sounds extreme. Are yours physically damaged beyond repair? Or just past his ability to fix it?

Rebuild kits are available but you should first understand the difference in a 'kit rebuild' vs. a major remanufacturing. Kits provide the gaskets and some mechanical parts to clean and restore an undamaged carb's functions. If you have major damage such as valve seat damage, body warp or broken out parts, no kit will fix them.

At that point you will have to determine whether to go for new or remanufacturing. I am not familiar with Rimco Machining. The bottom butterfly or throttle valves must open uniformly with both throttle position and in relation to the 2nd carb. Worn & sloppy throttle valves & linkage will cause running and idling problems. THat same principle is true of some FI systems and I did have a pair of triple throat stacks on a Porsche rebushed by Eurometrics with excellent success. (Porsche only sells replacement bodies.)

There are carb remanufacturers that will restore a carb to full OE specs. White Post Restorations (mentioned in the BRAKES forum) uses the Old Carb Doctor. With hundreds of National 1st and museum quality restorations, I trust their recommendations.

Old Carb Doctor
Rt 3 Box 338 Drucilla Church Rd.
Nebo, NC 28761

But DON'T expect that standard of work to be cheap. Geared primarily to remanufacturing obsolete carbs to new, the work is labor intensive and time consuming. The now-dated copy of the price list I have shows 'typical' European dual carbs at $300-350 a set but I note certain Zeniths at $600 per set.

Carb Doctor would disassemble a carb to its original component parts. Besides the normal rebuilding they would sleeve worn passages, insert new valve seats, restore the body and recalibrate to OE specs. Their work would include bushing and rebuilding worn throttle valves and linkages.

I can't believe anyone would even consider a chokeless carb in MN. First, '74s are EPA compliant vehicles and chokes are part of the regulated emmissions system. But more importantly, how the heck else are you expected to start the car in cold weather? Even the 'chokeless' carbs like some pre-EPA triple-throat Webers have a manual fuel enrichment mode. Nobody "likes" them because they require a modicum of intelligence to understand and repair them. But then my opinion of Muir's book matches its title -- for & from!

Never, ever run an engine without an air cleaner. One piece of debris can permanently damage an engine.

I don't know what you mean by "balance tube." That's not a VW part name. If you are talking the throttle activation rod that connects carbs, only one carb will work if it's missing; if you are talking the central idle system (Bentley 3-5) it won't idle or run properly without it (which would also affect starting.

Research your costs and options. Price new & rebuild carbs, VW & aftermarket. The site doesn't support parts "finding" so you'll have to do your own research, but there are a number of sources (& warnings) discussed on site. Do it right and enjoy a darn good power plant, or do it wrong and continue to suffer the consequences.
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New member
Ok - here's the situation - I've got a 1970 Campmobile that is in
good shape. It wasn' t running when I got it about four months ago,
but I was able to get it fired by adjusting the points, replacing
the condensor, plugs, and trying to time it as best I could by hand
without a timing light. It was running and holding an idle for a
while, but has since ceased to hold the idle. I have tried adjusting
the carb (30 PICT-30) by hand, adjusting both screws on the left
side of the carb. It seems that the fuel pump is still pumping well,
or at least pumping, the fuel cut-off solenoid clicks when I check
it, and I am at my wit's end trying to figure out what the problem
might be. I've removed and cleaned the carb, replaced the base
(manifold) gasket and top gasket, which did fix a fuel leak problem,
but that remedy has done nothing for the idle, or general running of
the engine. It runs great if I rev it, but not if I let the throttle
So my only thought for a solution is to call a mechanic, who perhaps
might be able to adjust the carb (idle and air control screws)
properly. I have one more theory I do want to bounce off of you
folks - via the Muir repair book, I disabled the automatic choke,
and perhaps did something wrong along the way. Since my bus is in
another city, I have not been able to test this theory, and perhaps
this is the problem, but I wanted to toss it out there before I
start to pull out my hair, or hand my bus over to someone I don't

Thanks for the help.


New member
hey there. i have friends campmobile to get started. the problem i am facing is this. the carb is leaking gas from the front of the carb.lower body. it appears that there is a valve that when i open the throttle manually it receeds into the body and the fuel comes out. i am not very experienced with this model and just want to know if that is normal and /or if a gasket or o-ring may need to be replaced; or the whold thing. thanks, melisa.

Capt. Mike

No fuel leaks are "normal". You have a serious defect and a safety hazard. However overhauling carbs is well covered in the Bentley shop manual, a requirement of the site.


New member
I have a 74 newly purchased (my first vw). The main carb on the stock configuration has been messed up by a previous owner. Stripped out the threads for the electromagnetic cut off valve and cut the tip off it after installing a heliarc insert.Ended up dumping fuel into the crankcase. Every one I talk to recommends going to a single Weber progressive carb. Is there a guideline for what size I need to go to? Also after looking thru vw mags is there a different requirement between type 2 and type 1? I am not a professional mechanic so i can use all the help I can get. Thanks.

Capt. Mike

Transferred to consolidate same topic.

vwphan Junior Member posted October 07, 2002 01:33 PM

I have been trying to get this done for a bit now and have no luck. It's a 72 bus with 74 dual carbs on it. My problem lies with the left carb. It has a large tube out the top which hooks into the air claeaner. Do i need to use the uni syn with this hose plugged or open. I did it open already, and although things seem better, now i get no response from the right carb when i turn anything. any advice on this would be great. thanks alot.


72 Sportsmobile with 77 westy interior and 73 914 engine

Capt. Mike

The left carb is your master carb and feeds the central idle system (Bentley 3-5; fig 5-3.). Adjustment (3-5.3) has some preparatory steps to complete first. Thus the right shouldn't affect idle that much. My experience with the dual carbs (on more than one vehicle) was that a good carb syncronizer (Unisyn brand is one) is essential and then must be done in the carb manuals procedure format. There are no shortcuts, and the rest of the engine must be correctly timed & tuned before you begin.

Once you start modifying a vehicle, you often have to go back to basic principles as nothing matches OE anymore. What is the hose to the air cleaner for? Is it the thermostatically controlled vacuum-operated flap (3-6, fig 6-3)? If so, it should be capped as it becomes a vacuum leak with the air cleaner removed for synchronizing.
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Capt. Mike

Transferred to consolidate same topic.

guzyk Junior Member posted December 22, 2002 10:43 PM

I have a 72 that has been converted to a single Weber and what appears to be a K&N filter.

When I bought the vehicle in June 2002, there was no hose between the carb (air cleaner) and the crankase. A shop I went to a couple months ago said "you need a hose connecting them or outside air etc will enter the engine". The shop installed a red rubber hose.

I recently noticed the air filter was very wet with oil (and it's not an oil bath filter) and the engine was burning a lot of oil. I assumed the carb was "sucking up the oil".


Anyway, the other day I chopped the hose, folded each end over and tied them up (essentially sealing the plug on the crankcase and the one on the carb).

Was this a stupid thing to do? What is the correct way to have a Weber/K&N setup on this type of motor?

Capt. Mike

Anytime you go to an aftermarket system, you can count on it failing to provide ALL of the OE functions. The OE fuel system was designed to provide not just fuel, but the necessary EPA and performance considerations such as crankcase breathing. It's probable your first system failed to allow the crankcase to properly breath, thus sucking oil into the air intake; and your solution will now block crankcase breathing, increasing pressure until you do more serious damage. The replacement carb is not the problem, it's you now no longer have all of the original fuel system working. You can continue with the aftermarket carb but will have to reinstall or manufacture the now defunct parts of the original fuel and venting system.

Capt. Mike

Bentley, 5-4, Fig 5-26 & 5-27 show the carburetors and the chokes. Note the dual carb system of the '72> uses a central idling system off the left carb that then feeds the right. There is an excellent trouble-shooting chart, 5-1, Table b.


New member
ok, so I pulled the carbs off, finding that there were no choke flaps for the ckokes to turn. So I found some and put them in. I have both carbs out still, and I've been doing some tests to them with a 12v motorcycle battery, hooking up the chokes and seeing how they work. And now I have some more questions.

1)One of the flaps is just a little bit sticky if you close it up all the way, and sometimes needs just a bit of a touch to get it unstuck to open. Would the air intake possibly take care of this when the carb is actually mounted?

2)The other carb's choke element will not open the flap completly from closed posistion (moves the flap about 30 degreas). The coil that contracts in the element when heated is a little lop sided, the center of the coil isn't the center of the element. I figured that it would still work, I just couldn't get the choke to go fully on if I want it to go off (and going off completly I guessed is important). Now maybe I should just get a new element, or maybe the diffrence is slight?

3)Also wondering if anyone knew how long it is normal for one of the elements to heat up and contract the coil fully? It's about 4-5 min on mine, but I know it's designed so that when you open the throttle, a little arm kicks the choke open a little.

4)How much does the air intake affect the posistioning of the flap? If it tends to open it a little or not that would be good to know.

Thanks for your help on everything. Its great to have a place like this to have your questions answered.


Capt. Mike

Obviously, they are not supposed to bind and that the flaps were missing is a strong indicator that the previous owner had screwed things up pretty good. The air intake valve, designed to insure warmed air during warm-up, has nothing to do with the choke -- it only determines where the supply air comes from.

I'm not trying to be derogatory, but it appears you don't have a lot of experience in fuel systems and carbs and are fighting a previously screwed up system without a lot of the necessary tools & facilities. The Bentley kindly puts it, Section 2-5.4, page 23, "If you lack the skills, tools or a suitable workshop for rebuilding the carburetor, we suggest you leave such repairs to an Authorized VW Dealer or other qualified shop." I'm not going to tout the local dealer who probably hasn't seen a carb in 20 years, but you can get rebuilt carbs from vendors on this web-site or can have them rebuilt to the highest degree of quality by some of the antique car restoration vendors such as The Carb Doctor, in Nebo, NC. When you have multiple symptoms and causes, sometimes it's best to bite the bullet, do one right and eliminate it from the rest of the troubleshooting. Carbs can be pretty arbitrary and very difficult to correct.


New member
won't start after warm 74 westy dual carb

Dear fellow Westy Owners:

Running the risk of posting out of turn, I have a challenge. I have been pouring over these threads and I haven't found one that answers my question.

My bus runs fine cold most of the time. Then, once in a while (and getting more frequent) the bus will not restart after a running for any length of time at operating temperature. I let it sit for a half hour, crank it and put the gas pedal to the floor and it will start. Then runs kinda rough for a few minutes. Then is OK.

I have replaced fuel filter, air filter, spark plugs and wires, points, cap, rotor and coil and changed the oil with lucas oil conditioner all for good measure since I bought the bus with no service history.

The problem existed before i changed out those parts.

I checked the current to the carb solenoids and they click as per the test in the manual. The right butterfly valve seems to stick a little on visual inspection with the air filter piece removed. I hope thats it. But it looks intimidating to me to pull the carb, open it up and tune once i put it back on.

Is there anything else I can do? If it were the fuel pump, wouldnt it crap out all the time, like never even start?

Any ideas? Thanks a ton for having this site. Im glad to have found it!

[Moderator note: Most probable is sticking or defective choke not resetting, Item 2, Table b. Bentley §3-5.1.]
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New member
carbs, timing, fule delivery

Thanks Capt. Mike.

Turns out with further testing, the fuel delivery to the carbs stops when the motor is hot. I pulled the gas inlet tube off the carb when cold, stuck the tube in a bottle and cranked the motor. There was about 2 oz of gas in the bottle after cranking for a few seconds. So I put the tube back on the carb cranked it up, drove around the neighborhood and then I let the bus idle in the driveway for about fifteen minutes or so until it died. Then I pulled the tube back off again, put it in the bottle and cranked it a few seconds again. This time, no fuel in the bottle. I ran it again this morning to the parts store to check out a temp gauge and got back in the bus to find it would not start. This time, I pulled the fuel to line to the carbs off the pump and put another tube to the bottle and cranked. Very little gas in the bottle.

It seems that the fuel pump craps out at high or running temps. Vapor lock in the fuel line is not really likely to me unless its in the pump.

I question wether or not the cooling flaps are open or closed. The bentley manual doesn't show how they are nested in home position or how they should look in the open position. There is however a very nice exploded iso graphic that shows all the parts. I can push on the cable mount on the flap rod downward and feel motion as well as pull on the cable from underneath and feel/hear the flaps move. i have also lubed the areas where the rod goes into the tin on left and right. I can not see where there are other hinges to lube. Perhaps something needs to be removed in order to do that.

I have read that I have to pull the motor to get to the fuel pump. On inspection, it looks like I might be able to pull a hose off and i could get at it the upper mounting bolt. Is this true? My thinking is I could get a generic electric pump rather than pull the engine.

I see the thermostat under the motor and it appears to have no change as the motor warms up. I fear that my engine is running way to hot because of the flap situation. That might be be the reason for the failure of the fuel pump. I have installed a new engine compartment seal completely around.

Should I also clean the fins on the oil cooler? is there supposed to be air flowing out from the bottom of the oil cooler? When I put my finger under it while the motor is running, I feel no air.

Am I on the right track? Is there any advise you can offer?

Thank you for your assistance.

Please advise.